This project will continue investigation on the elucidation of the metabolic pathway of neutral sterols to bile acids, especially regarding: a) the pathway from cholestanol to allo bile acids, b) the details of 12 alpha-hydroxylation of the sterol nucleus as related to the production of 5 alpha- and 5 beta-bile acids, c) improved systems of separation and quantitation of conjugated and free bile acids by HPLC, and improvement of a computerized data acquisition system for gas chromatographic-mass spectrometric identification of bile acids and their derivatives.